macOS: Respect window type when determining main window status

Fixes: QTBUG-84405
Change-Id: I3fc6b15b07a81e7e7e417a5767c2853083c13516
Reviewed-by: Timur Pocheptsov <timur.pocheptsov@qt.io>
(cherry picked from commit 1cd7cbf6179692fc824dc3ba15580372493a4355)
Reviewed-by: Jani Heikkinen <jani.heikkinen@qt.io>

src/plugins/platforms/cocoa/qnswindow.mm

@@ -227,14 +227,12 @@ static bool isMouseEvent(NSEvent *ev)
 
 - (BOOL)canBecomeMainWindow
 {
-    BOOL canBecomeMain = YES; // By default, windows can become the main window
-
     // Windows with a transient parent (such as combobox popup windows)
     // cannot become the main window:
     if (!m_platformWindow || m_platformWindow->window()->transientParent())
-        canBecomeMain = NO;
+        return NO;
 
-    return canBecomeMain;
+    return [super canBecomeMainWindow];
 }
 
 - (BOOL)worksWhenModal